The Hemodynamic Mass Action of a Central Pattern Generator

Abstract

The hemodynamic response is a neurovascular and metabolic process in which there is rapid delivery of blood flow to a neuronal tissue in response to neuronal activation. The functional magnetic resonance imaging (fMRI) and the functional near-infrared spectroscopy (fNIRS), for instance, are based on the physiological principles of such hemodynamic responses. Both techniques allow the mapping of active neuronal regions in which the neurovascular and metabolic events are occurring. However, although both techniques have revolutionized the neurosciences, they are mostly employed for neuroimaging of the human brain but not for the spinal cord during functional tasks. Moreover, little is known about other techniques measuring the hemodynamic response in the spinal cord. The purpose of the present study was to show for the first time that a simple optical system termed direct current photoplethysmography (DC-PPG) can be employed to detect hemodynamic responses of the spinal cord and the brainstem during the functional activation of the spinal central pattern generator (CPG). In particular, we positioned two DC-PPG systems directly on the brainstem and spinal cord during fictive scratching in the cat. The optical DC-PPG systems allowed the trialby-trial recording of massive hemodynamic signals. We found that the "strength" of the flexor-plus-extensor motoneuron activities during motor episodes of fictive scratching was significantly correlated to the "strengths" of the brainstem and spinal DC-PPG signals. Because the DC-PPG was robustly detected in real-time, we claim that such a functional signal reflects the hemodynamic mass action of the brainstem and spinal cord associated with the CPG motor action. Our findings shed light on an unexplored hemodynamic observable of the spinal CPGs, providing a proof of concept that the DC-PPG can be used for the assessment of the integrity of the human CPGs.

Beyond life: Exploring hemodynamic patterns in postmortem mice brains

“…The time series of LSCI images of the mouse brain obtained postmortem, as well as those processed using FFT, CWT, and NMF, show that the distribution of cerebral blood flow is highly non‐homogeneous, with pronounced spatial and temporal hemodynamic localizations (see Figures 1 and 2, and associated Video S1). In line with previous studies that demonstrate a strong spatial relationship between hemodynamic changes and neural activity [36–38], also known as neurovascular coupling [39], the identified localizations of cerebral blood flow and blood microcirculation have been compared with a confirmed anatomical template and corresponding neuroanatomical domains [40]. The results obtained through LSCI, FFT, CWT, and NMF (see Figures 1 and 2, and Video S1) clearly reveal predominant hemodynamic localization in the olfactory bulbs.…”

Beyond Life: Exploring Hemodynamic Patterns in Postmortem Mice Brains

“…The time series of LSCI images of the mouse brain obtained postmortem, as well as those processed using In line with previous studies that demonstrate a strong spatial relationship between hemodynamic changes and neural activity [28][29][30], also known as neurovascular coupling [31], the identified localizations of cerebral blood flow and blood microcirculation have been compared with a confirmed anatomical template and corresponding neuroanatomical domains [32]. The results obtained through LSCI, FFT, CWT, and NMF (see ).…”